1. Field of the Invention
The present invention relates to a process and a system for painting a vehicle body.
2. Description of Related Art
Painting a vehicle body, in particular an exterior body panel of a vehicle body that has a demand for attractive exterior appearance and durability properties, typically comprises an undercoat, an intermediate coat and an overcoat. The undercoat is often applied by electrodepositing a coating composition so as thereby to form an undercoat layer and finished by baking and drying the undercoat layer. The intermediate coat is applied by spraying a coating composition over the undercoat layer that has been baked and dried so as to form an intermediate layer, and then finished by baking and drying the intermediate coat layer. Finally, the overcoat is applied by spraying a coating composition over the intermediate coat layer that has been baked and dried so as to form an overcoat layer, and then finished by baking and drying the overcoat layer.
Application of coat for the overcoat of the vehicle body is not confined to only once and the number of times of the application of coat for the overcoat depends upon the type of coating composition and the grade of finish. For example, when using one selected from a group of solid coating compositions, the application of coat for the overcoat is often made only once. However, in the case where the overcoat is completed by applying a coat of a coating composition selected from the group of metallic coating compositions two times, a base coat of a color coating composition containing a metallic powder is applied first and then a clear coat is applied over the color base coat layer. Otherwise, a solid type coating composition is sometimes employed for the color base coat in place of the metallic powder contained coating composition. One of examples in which the overcoat is completed by applying a coat three times is the case of an overcoat comprising a bright coat. Specifically, after a coating composition for the color base coat that contains a metallic powder is applied first, a bright base coat is applied, and a clear coat is subsequently applied to finish the overcoat. In these multiple coating processes, the overcoat is performed by what is called a wet-on-wet application. That is, a succeeding coat is applied over the last coat layer which has not yet been dried, in other words, which remains still wet. The overcoat layers formed in the wet-on-wet application are finally baked and dried all together in an oven.
In the multiple coating processes including an application of a brightener material contained coating composition such as a coating composition containing mica, while a color base coat layer without containing a brightener material remains wet, a brightener material contained coating composition is sprayed so as to form a bright coat layer over the color base coat layer and then a coating material is applied so as to form a clear coat layer over the bright base coat layer that remains wet. These three coat layers are baked and dried all together in an oven. Such a process, that is called three coats-simultaneous baking process, is disclosed, for example, in Japanese Unexamined Patent Publication No. 10-277478.
As disclosed, for example, in Japanese Unexamined Patent Publication No. 10-296178, when using the three coats-simultaneous baking process for forming an overcoat by spraying a coating composition containing a brightener material to exterior body portion, the overcoat is completed in specific steps of spraying coating compositions in relation to a coat applied to an interior door portion (interior portions near a door). That is, an application of a color base coat to the interior door portion and thereafter to the exterior body portion, an application of a mica base coat to the exterior body portion and an application of a clear coat to the interior door portion and thereafter to the exterior body portion are sequentially performed in the wet-on-wet application in this order. All the coat layers formed on the exterior body portion and the interior door portion are simultaneously baked and dried together. The three-coats simultaneous baking process always has the necessity of both an application of an intermediate coat prior to an application of the overcoat and baking and drying the intermediate coat layer in advance of the application of the overcoat like the conventional painting processes.
It is also known, for example, from Japanese Unexamined Patent Publication No. 10-216617, that a color base coat is applied to form a color base coat layer over an intermediate coat layer that remains wet and then a clear coat is applied to form a clear coat layer over the color base coat layer that remains wet, and all the three coat layers are finally baked and dried together.
Meanwhile, as for the vehicle body painting, although the overcoat of the exterior body portion is of the most importance in view of attractive exterior appearance and durability properties, it is also necessary to paint an interior door portion, an engine compartment, a cargo compartment, etc. The interior door portion also has a demand for attractive interior appearance and also a demand for finished color and quality similar to those of the exterior body portion as the interior door portion is eye catching for occupants of the vehicle and conspicuous when the doors are open. Therefore, the overcoats applied to the interior door portion and the exterior body portion are generally identical in color and quality with each other.
Since the engine and cargo compartments are kept out of sight, there is less demand for attractive exterior appearance and durability properties, it is suffice for the coat of the engine and/or cargo compartments to be identical in color with or similar in color to the exterior body portion.
In designing vehicle body painting, it is necessary to consider an overspray problem in addition to respective coating requirements of the exterior body portion, the interior door portion and the engine and/or cargo compartments. That is, when applying a coat the exterior body portion, a coating composition is sprayed more than a little on the interior door portion and the engine and cargo compartments. A similar overspray problem occurs when applying a coat to the interior door portion or the engine and/or cargo compartments.
One aspect of the overspray problem is color mixing. That is, when a coat layer is partly sprayed with a coating composition, the part of the coat layer is mingled in color with the coating composition and is stained differently from the remaining part. Another aspect of the overspray problem is a defect of paintwork (a deterioration in the flatness and smoothness of coat layer). The defect of paintwork becomes marked when a coating composition is sprayed on a coat layer having been backed and dried once. However, the defect of paintwork is practically insignificant when a coating composition is sprayed on a coat layer remaining wet. This is because the coating composition is fused together with the coat layer before long.
In order to avoid the color mixing, a color intermediate coat is often applied by spraying a coating composition having a color identical with or similar to the overcoat. Specifically, while it is desirable to employ a gray coating composition for the intermediate coat from the viewpoint of cost, it is general in turn to apply a color intermediate coat to both the exterior body portion and the engine and/or cargo compartments for the purpose of preventing an occurrence of color mixing due to an overspray or to the engine and/or cargo compartments only. Further, it is expensive but effective to apply not intermediate coat but a color base coat that forms a part of an overcoat to the engine and/or cargo compartments.
If the step of baking and drying an intermediate coat layer that is essential in the conventional painting processes can be dispensable, the painting process offers a lot of advantages in terms of costs for installation of printing equipments and running costs. In addition, the painting process can be made intensive, so as to be contributive to increasing the design flexibility of manual or automatic painting works. This makes it possible to reduce painting costs more effectively. These advantages are more enhanced in the case where an application of an intermediate coat to the interior door portion is dispensed.
It is therefore an object of the present invention to provide a vehicle body painting process and system which eliminates the overspray problem and the step of baking and drying exclusively an intermediate coat layer with an effect of inexpensive and efficient vehicle body painting.
The foregoing object of the present invention is accomplished by a vehicle body painting process in which an intermediate coat and an overcoat are made in a wet-on-wet application and intermediate coat and overcoat layers are baked and dried all together.
According to a preferred embodiment of the present invention, the vehicle body painting process of painting a vehicle body comprising an exterior body portion, engine and cargo compartments and an interior door portion includes an application of an intermediate coat and an overcoat comprising at least a color base coat and a clear coat to at least the exterior body portion. The vehicle body painting process comprises the steps of a first coating step of applying said intermediate coat to said exterior body portion, a second coating step of applying with the intermediate coat to at least one of the engine and cargo compartments after the first coating step, a third coating step of applying the color base coat to the interior door portion at least after the first coating step, a fourth coating step of applying the color base coat to the exterior body portion after both the second coating step and the third coating step, a fifth coating step of applying the clear coat to the interior door portion after the fourth coating step, a sixth coating step of applying the clear coat to the exterior body portion at least after the fourth coating step; and a baking and drying step of baking and drying coat layers formed in the first through sixth coating steps after both the fifth coating step and the sixth coating step, wherein each of the second to sixth coating steps is made while the coat layers formed in the coating steps preceding the each coating step remain wet and the intermediate coat applied to the engine and cargo compartments is identical with either one of the intermediate coat and the color base coat and has a color identical with or similar to the color base coat. A coating composition such as selected from a group of brightener contained coating compositions and a group of solid coating compositions may be employed for the color base coat.
The vehicle body painting process has no necessity of baking and drying exclusively the intermediate coat layers, and hence eliminates installation of a baking and drying oven exclusive for the intermediate coat layers in a painting system, so that the painting process is advantageous in terms of costs for installation of printing equipments and running costs. In addition, since all coats are performed in the wet-on-wet application after an application of the intermediate coat, there occurs no defect of paintwork due to an overspray problem. Furthermore, the vehicle body painting process is made intensive resulting from the elimination of the step of baking and drying the intermediate coat layer and an application of the intermediate coat to the interior door portion, so as to increase the design flexibility of manual or automatic painting works and, in consequence, to reduce painting costs more effectively.
Application of coat to the interior door portion, the engine compartment or the cargo compartment is made by spraying a coating composition to the vehicle body from opposite sides, namely left and right spray booths in each coating station. The left and right spray booths are generally displaced from each other in a vehicle body carrying direction in which the vehicle body is carried so as to prevent a spray device operator at one of the spray booths from being dabbed with an overspray of coating composition from a spray device in the other spray booth. Although this displaced layout of the spray booths produces dead spaces in the vehicle body carrying direction, the number of dead spaces is four in total in the printing system which is quite small.
According to another preferred embodiment of the present invention, the vehicle body painting process of painting a vehicle body comprising an exterior body portion, engine and cargo compartments and an interior door portion includes an application of an intermediate coat and an overcoat comprising at least a color base coat, a bright base coat and a clear coat to at least the exterior body portion. The vehicle body painting process comprises the steps of a first coating step of applying an intermediate coat to the exterior body portion, a second coating step of applying an intermediate coat to at least one of the engine and cargo compartments after the first coating step, a third coating step of applying the color base coat to the interior door portion at least after the first coating step, a fourth coating step of applying the color base coat to the exterior body portion after both the second coating step and third coating step, a fifth coating step of applying the bright base coat to the exterior body portion after the fourth coating step, a sixth coating step of applying the bright base coat to the interior door portion at least after the fourth coating step, a seventh coating step of applying the clear coat to the interior door portion after both the fifth coating step and the sixth coating step, a eighth coating step of applying the clear coat to the exterior body portion after both the fifth coating step and the sixth coating step, and a baking and drying step of baking and drying coat layers formed in the first through eighth coating steps after both the seventh coating step and the eighth coating step, wherein each of the second to eighth coating steps is made while the coat layers formed in the coating steps preceding the each coating step remain wet and the intermediate coat applied to the engine and cargo compartments is identical with either one of the intermediate coat and the color base coat and has a color identical with or similar to the color base coat. A coating composition for the bright base coat may contain mica as a brightener material.
Like the previous embodiment, the vehicle body painting process has no necessity of baking and drying exclusively the intermediate coat layers, and hence eliminates installation of a baking and drying oven exclusive for the intermediate coat layers in a painting system, so that the painting process is advantageous in terms of costs for installation of printing equipments and running costs. In addition, since all coats are performed in the wet-on-wet application after an application of the intermediate coat, there occurs no defect of paintwork due to an overspray problem. Furthermore, the vehicle body painting process is made intensive resulting from the elimination of the step of baking and drying the intermediate coat layer and an application of the intermediate coat to the interior door portion, so as to increase the design flexibility of manual or automatic painting works and, in consequence, to reduce painting costs more effectively.
According to still another preferred embodiment of the present invention, the vehicle body painting process of painting a vehicle body comprising an exterior body portion, engine and cargo compartments and an interior door portion includes an application of an intermediate coat and an overcoat comprising at least a color base coat and a clear coat to at least the exterior body portion. The vehicle body painting process comprises the steps of a first coating step of applying the intermediate coat to the exterior body portion, a second coating step of applying the intermediate coat to at least one of the engine and cargo compartments after the first coating step, a third coating step of applying the intermediate coat to the interior door portion at least after the first coating step, a fourth coating step of applying the color base coat to the exterior body portion after both the second coating step and the third coating step, a fifth coating step of applying the color base coat to the interior door portion after both the second coating step and third coating step, a sixth coating step of applying the clear coat to the interior door portion after both the fourth coating step and the fifth coating step, a seventh coating step of applying the clear coat to the exterior body portion after both the fourth coating step and the fifth coating step, and a baking and drying step of baking and drying coat layers formed in the first through seventh coating steps after both the sixth coating step and the seventh coating step, wherein each of the second to seventh coating steps is made while the coat layers formed in the coating steps preceding the each coating step remain wet and the intermediate coat applied to the engine and cargo compartments is identical with either one of the intermediate coat and the color base coat and has a color identical with or similar to the color base coat. In this embodiment, a coating composition such as selected from a group of brightener contained coating compositions and a group of solid coating compositions may be employed for the color base coat.
Like the previous embodiments, the vehicle body painting process has no necessity of baking and drying exclusively the intermediate coat layers, and hence eliminates installation of a baking and drying oven exclusive for the intermediate coat layers in a painting system, so that the painting process is advantageous in terms of costs for installation of printing equipments and running costs. In addition, since all coats are performed in the wet-on-wet application after an application of the intermediate coat, there occurs no defect of paintwork due to an overspray problem. Furthermore, the vehicle body painting process is made intensive resulting from the elimination of the step of baking and drying the intermediate coat layer and an application of the intermediate coat to the interior door portion, so as to increase the design flexibility of manual or automatic painting works and, in consequence, to reduce painting costs more effectively.
In the respective embodiments, the application of the color base coat to the interior door portion may be made directly after the application of the intermediate coat to the engine and cargo compartments. In this instance, there occurs no overspray problem in connection with the interior door portion upon an application of the intermediate coat to the engine and/or cargo compartment. This is desirable to finish the exterior body portion to a satisfactory paintwork properties.
Further, a coating composition for the intermediate coat applied to the exterior body portion may be gray in color. In this instance, inexpensive coating compositions can be employed for the intermediate coat. In addition, a coating composition for the intermediate coat applied to the engine and/or cargo compartments may be identical with that for the color base coat. This makes it possible to employ inexpensive coating compositions for the engine and/or cargo compartments that are identical in color with the exterior body portion.
In the second embodiment, the application of the bright base coat to the interior door portion may be made directly after the application of the bright base coat to the exterior body portion. In this instance, the vehicle body painting system has a significantly small number of, specifically only four, dead spaces in the vehicle body carrying direction. The applications of the bright base coat to the interior door portion and the application of the bright base coat to the exterior body portion may be made in reverse order. In this instance, since the same coating composition is sprayed on the exterior body portion prior to the interior door portion, this is desirable to finish the exterior body portion to a satisfactory paintwork properties.
In the third embodiment of the present invention, the application of the color base coat to the interior door portion may be made directly after the application of the color base coat to the exterior door portion. In addition, the application of the intermediate coat to the interior door portion and the application of the color base coat to the exterior body portion may be made directly after the application of the intermediate coat to the engine and cargo compartments and the application of the intermediate coat to the interior door portion, respectively. This is contributory to laying out the vehicle body painting system so as to have dead spaces as small in number as possible.
Furthermore, the application of the color base coat to the exterior body portion may be made directly after the application of the color base coat to the interior door portion. This is desirable to finish the exterior body portion to a satisfactory paintwork properties.
According to a further preferred embodiment of the present invention, the vehicle body painting process of painting a vehicle body comprising an exterior body portion, engine and cargo compartments and an interior door portion includes an application of an intermediate coat and an overcoat comprising at least a color base coat and a clear coat to at least the exterior body portion. The vehicle body comprising an exterior body portion, engine and cargo compartments and an interior door portion includes an application of an intermediate coat and an overcoart comprising at least a color base coat to at least the exterior body portion. The vehicle body painting process comprising the steps of a first coating step of applying the intermediate coat to the exterior body portion, a second coating step of applying the intermediate coat to at least one of the engine and cargo compartments after the first coating step, a third coating step of applying the color base coat to the interior door portion at least after the first coating step, a fourth coating step of applying the color base coat to the exterior body portion after both the second coating step and the third coating step, and a baking and drying step of baking and drying coat layers formed in the first through fourth coating steps after the fourth coating step, wherein each of the second to fourth coating steps is made while the coat layers formed in the steps preceding the each step remain wet, a coating composition for the color base coat comprises one selected from a group of solid coating compositions, and the intermediate coat applied to the engine and cargo compartments is identical with either one of the intermediate coat and the color base coat and has a color either identical with or similar to the color base coat.
The vehicle body painting process has no necessity of baking and drying exclusively the intermediate coat layers, and hence eliminates installation of a baking and drying oven exclusive for the intermediate coat layers in a painting system, so that the painting process is advantageous in terms of costs for installation of printing equipments and running costs. In addition, since all coats are performed in the wet-on-wet application after an application of the intermediate coat, there occurs no defect of paintwork due to an overspray problem. Furthermore, the vehicle body painting process is made intensive resulting from the elimination of the step of baking and drying the intermediate coat layer and an application of the intermediate coat to the interior door portion, so as to increase the design flexibility of manual or automatic painting works and, in consequence, to reduce painting costs more effectively.
On the other hand, the foregoing object of the present invention is accomplished by a vehicle body painting system for carrying out the vehicle body painting process according to each of the preferred embodiments.
According to a preferred embodiment of the present invention that realizes the vehicle body painting process of the first embodiment, the vehicle body painting system for painting a vehicle body comprising an exterior body portion, engine and cargo compartments and an interior door portion includes a plurality of coating stations through which an intermediate coat and an overcoat comprising at least a color base coat and a clear coat are applied to at least the exterior body portion.
Specifically, the vehicle body painting system comprises a first coating station where application of an intermediate coat to the exterior body portion is made, a second coating station where either one of an application of the color base coat to the interior door portion and an application of the intermediate coat to the engine and cargo compartments is made, a third coating station where another one of the application of the color base coat to the interior door portion and the application of the intermediate coat to the engine and cargo compartments is made, a fourth coating station where an application of the color base coat to the exterior body portion, a fifth coating station where an application of the clear coat to either one of the interior door portion and the exterior body portion, a sixth coating station where an application of the clear coat to another one of the interior door portion and the exterior body portion, and a baking and drying station where coat layers formed in the first through fifth stations are baked and dried, wherein each of the applications of coat in the first to sixth stations is made while the coat layers formed in the coating stations preceding each the application of coat remain wet and the intermediate coat applied to the engine and cargo compartments is identical with either one of the intermediate coat and the color base coat and has a color identical with or similar to the color base coat.
According to another preferred embodiment of the present invention that realizes the vehicle body painting process of the second embodiment, the vehicle body painting system for painting a vehicle body comprising an exterior body portion, engine and cargo compartments and an interior door portion includes a plurality of coating stations through which an intermediate coat and an overcoat comprising at least a color base coat, a bright base coat and a clear coat are applied to at least the exterior body portion.
Specifically, the vehicle body painting system comprises a first coating station where application of an intermediate coat to the exterior body portion is made, a second coating station where either one of an application of the color base coat to the interior door portion and an application of the intermediate coat to the engine and cargo compartments is made, a third coating station where another one of the application of the color base coat to the interior door portion and the application of the intermediate coat to the engine and cargo compartments is made, a fourth coating station where an application of the color base coat to the exterior body portion, a fifth coating station where an application of the bright base coat to either one of the exterior body portion and the interior door portion, a sixth coating station where an application of the bright base coat to another one of the exterior body portion and the interior door portion, a seventh coating station where an application of the clear base coat to either one of the exterior body portion and the interior door portion, a eighth coating station where an application of the clear base coat to another one of the exterior body portion and the interior door portion, and a baking and drying station where coat layers formed in the first through eighth stations are baked and dried, wherein each of the applications of coat in the second to eighth coating stations is made while the coat layers formed in the coating stations preceding the each the application of coat remain wet and the intermediate coat applied to the engine and cargo compartments is identical with either one of the intermediate coat and the color base coat and has a color identical with or similar to the color base coat.
According to still another preferred embodiment of the present invention that realizes the vehicle body painting process of the third embodiment, the vehicle body painting system for painting a vehicle body comprising an exterior body portion, engine and cargo compartments and an interior door portion includes a plurality of coating stations through which an intermediate coat and an overcoat comprising at least a color base coat and a clear coat are applied to at least the exterior body portion.
Specifically, the vehicle body painting system comprises a first coating station where an application of the intermediate coat to the exterior body portion, a second coating station where either one of an application of the color base coat to the interior door portion and an application of the intermediate coat to the engine and cargo compartments is made, a third coating station where another one of the application of the color base coat to the interior door portion and the application of the intermediate coat to the engine and cargo compartments is made, a fourth coating station where an application of the color base coat to either one of the exterior body portion and the interior door portion, a fifth coating station where an application of the color base coat to another one of the exterior body portion and the interior door portion, a sixth coating station where an application of the clear coat to either one of the exterior body portion and the interior door portion is made, a seventh coating station where an application of the clear coat to another one of the exterior body portion and the interior door portion; and a baking and drying stations where coat layers formed in the first through seventh coating stations are baked and dried; wherein each of the applications of coat in the second to eighth coating stations is made while the coat layers formed in the coating stations preceding the each the application of coat remain wet and the intermediate coat applied to the engine and cargo compartments is identical with either one of the intermediate coat and the color base coat and has a color identical with or similar to the color base coat.
According to a further preferred embodiment of the present invention that realizes the vehicle body painting process of the fourth embodiment, the vehicle body painting system for painting a vehicle body comprising an exterior body portion, engine and cargo compartments and an interior door portion includes a plurality of coating stations through which an intermediate coat and an overcoat comprising at least a color base coat and a clear coat are applied to at least the exterior body portion.
Specifically, the vehicle body painting system comprises a first coating station where an application of the intermediate coat to the exterior body portion, a second coating station where either one of an application of the color base coat to the interior door portion and an application of the intermediate coat to the engine and cargo compartments is made, a third coating station where another one of the application of the color base coat to the interior door portion and the application of the intermediate coat to the engine and cargo compartments is made, a fourth coating station where an application of the color base coat to the exterior body portion, and a baking and drying station where coat layers formed in the first through fourth coating stations are baked and dried, wherein each of the applications of coat in the second to fourth coating stations is made while the coat layers formed in the coating stations preceding the each application of coat remain wet, a coating composition for the color base coat comprises one selected from a group of solid coating compositions, and the intermediate coat applied to the engine and cargo compartments is identical with either one of the intermediate coat and the color base coat and has a color either identical with or similar to the color base coat.